A memory resistor is a device that exhibits a switchable resistance state such that the same applied voltage to the memory resistor can produce different responses from the memory resistor depending on the memory resistor's resistance state. When the memory resistor exhibits a resistance state corresponding to a high resistance, an application of a given voltage across the memory resistor will draw a relatively lower current than would a memory resistor that exhibits a resistance state corresponding to a relatively lower resistance if the same voltage is applied thereto.
Examples of memory resistors include unipolar memory resistors and bipolar memory resistors. With a unipolar memory resistor, applied voltages of the same polarities (but different magnitudes, e.g., VON and VOFF) are used to switch the memory resistor between different states. With a bipolar memory resistor, applied voltages of different polarities (and of sufficient magnitude) are used to switch the memory resistor between different states.
Given these properties, memory resistors can be used as memory cells where the resistance state can be used to denote a logical “1” or “0” for data storage. Moreover, because the resistance state of the memory resistor can retain its current resistance state in the absence of an applied voltage, memory resistors can be used for nonvolatile data storage.